PROJECT SUMMARY/ABSTRACT The proposed research builds on our prior 14-year achievements investigating the role of new immunologic biomarkers and genetic factors that provide a more accurate staging of Type 1 diabetes (T1D). Recently our laboratory discovered two novel autoantibody biomarkers, IA-2 variant-specific (IA-2var) and IA-2 extracellular (IA-2ec) domain autoantibodies. In particular, we identified variant-specific IA-2 autoantibodies (IA-2var) incorporating amino acid residue variants (Cys27, Gly608 and Pro671) in the full length molecule and developed new bioassays detecting autoantibodies and T cell responses against the IA-2var molecule. We provided preliminary data indicating that the newly identified IA-2var autoantibodies, in combination with HLADQ/DR genotypes, significantly improves risk prediction in first-degree relatives of T1D patients (Figure 4, 5). We will utilize these biomarkers in the population of the Diabetes Prevention Trial-Type 1 (DPT-1) Study, which is based on deeply phenotyped individuals, longitudinally followed and characterized with respect to multiple islet-related autoantibodies, HLA genotypes, and other risk factors (Specific Aim I). The DPT-1 Study is a unique resource for innovative research on new T1D biomarkers, and a catalyst for the exchange of knowledge and collaboration and many critical studies on T1D prediction have been conducted in this population. We will be using the Illumina Global Screening Array (GSA) in collaboration with Dr. Stephen Rich who pioneered seminal studies in the genetics of T1D and other autoimmune disorders. We hypothesize that the progression to T1D in relatives carrying IA-2var autoantibodies and SNPs in genes covered by the GSA, including HLA DQ/DR-tagging variants, are highly predictive of T1D progression (Specific Aim I). The availability of our recently identified IA-2 autoantibody biomarkers led to the identification of new T cell epitopes within the IA-2 extracellular domain (manuscript under review). In silico molecular modeling and docking of IA-2 peptides to HLA class II molecules suggests that there are high affinity epitopes for both HLA DQ8 and DR4 which confer significant genetic risk for T1D (Figure 8, 9). We hypothesize that IA-2 peptides within the IA-2var and the extracellular domain that exhibit enhanced binding to disease susceptible HLA molecules will elicit robust CD4+ T cell responses (Specific Aim II). These disease-specific T cells could be feasible targets of immunotherapies while the epitopes offer the potential of antigen specific therapies to prevent or ameliorate the disease course. This investigation will add to our knowledge of the natural history of T1D and motivate the development and implementation of prevention trials for T1D.